CA1157910A - Method of generating electricity using an endothermic coal gasifier and mhd generator - Google Patents
Method of generating electricity using an endothermic coal gasifier and mhd generatorInfo
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- CA1157910A CA1157910A CA000382684A CA382684A CA1157910A CA 1157910 A CA1157910 A CA 1157910A CA 000382684 A CA000382684 A CA 000382684A CA 382684 A CA382684 A CA 382684A CA 1157910 A CA1157910 A CA 1157910A
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- gases
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- diffuser
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K44/00—Machines in which the dynamo-electric interaction between a plasma or flow of conductive liquid or of fluid-borne conductive or magnetic particles and a coil system or magnetic field converts energy of mass flow into electrical energy or vice versa
- H02K44/08—Magnetohydrodynamic [MHD] generators
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- Fluid Mechanics (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Air Supply (AREA)
- Engine Equipment That Uses Special Cycles (AREA)
- Hydrogen, Water And Hydrids (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A system and method of generating electrical power wherein a mixture of carbonaceous material and water is heated to initiate and sustain the endothermic reaction of carbon and water thereby providing a gasified stream con-taining carbon monoxide, hydrogen and nitrogen and waste streams of hydrogen sulfide and ash. The gasified stream and an ionizing seed material and pressurized air from a preheater go to a burner for producing ionized combustion gases having a temperature of about 5000 to about 6000°F.
which are accelerated to a velocity of about 1000 meters per second and passed through an MHD generator to generate DC power and thereafter through a diffuser to reduce the velocity. The gases from the diffuser go to an afterburner and from there in heat exchange relationship with the gasi-fier to provide heat to sustain the endothermic reaction of carbon and water and with the preheater to preheat the air prior to combustion with the gasified stream. Energy from the afterburner can also be used to energize other parts of the system.
A system and method of generating electrical power wherein a mixture of carbonaceous material and water is heated to initiate and sustain the endothermic reaction of carbon and water thereby providing a gasified stream con-taining carbon monoxide, hydrogen and nitrogen and waste streams of hydrogen sulfide and ash. The gasified stream and an ionizing seed material and pressurized air from a preheater go to a burner for producing ionized combustion gases having a temperature of about 5000 to about 6000°F.
which are accelerated to a velocity of about 1000 meters per second and passed through an MHD generator to generate DC power and thereafter through a diffuser to reduce the velocity. The gases from the diffuser go to an afterburner and from there in heat exchange relationship with the gasi-fier to provide heat to sustain the endothermic reaction of carbon and water and with the preheater to preheat the air prior to combustion with the gasified stream. Energy from the afterburner can also be used to energize other parts of the system.
Description
~ 1S791~
ME:THOD OF GENER~TING ELECTRICITY USI~G AN
ENDOTHE~MIC COAL GASIFIER AND MHD GE21ERATOR
BACKGROUND OF THE INVENTION
The development of the magnetohydrodynamic (MHD) generator has been considered important because of several advanta~es. These include a low capital cost, greater efficiency of heat conversion to electrical energy and rapid start-up. The development of the MHD generator has been hampered by several problems, especially in the case of coal combustion. Among these problems are the effect of ash on the process equipment, the removal of the ash and separation of the ash or coal slag from khe seed. Low combustion temperatures which require the necessity of pre-heating air to the burner and the low overall MHD efficiency due to the high energy content of the effl-lent gases from the MHD generator pose additional problems.
In general terms, MHD generators produce electrical power by movement of electr-ically conductive fluid relative to a magnetlc field. The fluid employed is usually an electrically conductive gas from a high temperature, high pressure source. From the source, the fluid flows through the generator and, by virtue of its movement relative to the magnetic field, induces an electromotive force between opposed electrodes in the generator. The gas may exhaust to a sink which may simply be the atmosphere; or, in a more sophisticated system, the gas may exhaust to a reco-very system including pumping mechanism for returning the gas to the source.
~everal different gases may be used; the gas may be products of combustion, or may comprise inert gases such as helium or argon. In open systems, such as those in which the gases are not recycled after passing through the power plant, products of combustion are normally used. In closed systems, in which the gases are recycled, it is feasible to use relatively expensive gases, such as helium and argon.
To promote electrical conductivity, the gases are heated to a high temperature; conductivity is also increased by the addition to the gases of a substance that ionizes readily at the operating temperatures of the generator. Regardless of the gas used, the gas includes a mixture of electrons, positive ions and neutral atoms which, for convenience, is usually termed "plasma".
The temperature of the plasma is highly significant, not only to the overall efficiency of the systen~ but also to the design of the MHD generator. With a higher temperature available at the inlet of the generator, a larger isentropic drop can be developed as the plasma expands through the generator, resulting in an improved plant efficiency.
` ` 1 157910 Because the electrical conductivity of the plasma increases as the temperature increases, it is possible to generate a given amount of power in a relatively smaller generator and employ a smaller magnetic field than would otherwise be - possible with employment of increased temperatures. The increased efficiency of the MHD system, considerably above that of conventional steam turbine plants, coupled with the absence of hot moving parts in the generator suggest that in time MHD power plants will replace or substantially sup-plant power generating systems of conventional design.
Some of the problems endemic to MHD systems, even after the substantial amount of development work over the past several years includes the loss of high energy gas from the MHD generator as well as the necessity to preheat air in order to obtain the requisite high temperatures at the generator inlet and to dry and preheat the fuel, particularly where coal is employed.
~epresentative literature relating to MHD generating systems includes U.S. Patent No. 3,414,744 issued December 3, 1968 to Petrick for Magnetohydrodynamic Generator which discloses the use of an r~HD generator using Na~ coolant from a nuclear reactor.
U.S. Patent No. 3,531,665 issued September 29, 1970 to Rosa for Coal Preheating System For Magnetohydrodynamic Devices which discloses mechanism for preheating pulverized coal with MHD off gas.
U.S. Patent No. 3,720,850 issued March 13, 1973 to T~ay for Magnetohydrodynamic Power System With Semi-Closed ` 1 157910 Cycle shows the recycling of MHD off gases to the inlet side of the MHD generator.
U.S. Patent No. 3,873,845 issued March 25, 1975 to Osthaus for Method Of Producing Electric Energy Including Coal Gasification discloses a process and system for gasi-fying coal dust with air heated to 1500C., the combustion gas therefrom being cooled to 150C. thereby producing high pressure steam for producing electricity.
U.S. Patent No. 3,895,243 issued July 15, 1975 to Amend et al. for Method And Means Of Generating Power From Fossil Fuels With A Combined Plasma And Liquid-Metal MHD
Cycle discloses a process for utili~ing the waste heat from a fossil fuel MHD generator to heat a llquid-metal MHD
generator. Air is preheated ~y heat exchange with the walls of the combustion chamber for the MHD generator.
U.S. Patent No. 4,064,222 issued December 23, 1977 to Bretz for Nitrogen Fixation And Molecular Magneto Hydro-dynamic Generation Using A Coal Gasification Gas Stream discloses a coal gasifier using coal and oxygen to produce off gas which is burned wi~h air and fed to a MHD generator followed by adiabat~c expans~on to fix the nitrogen oxides.
U.S. Patent ~o. 4,107,557 issued August 15, 1978 to Shepard for Sulfur-Fueled Magnetohydrodynamic Power Genera-tion discloses a closed cycle MHD generator using sulfur and oxygen to produce a flame temperature of greater than 8000F. to the MHD generator.
SUMMARY OF THE INVENTION
This invention relates to a method and system of generating electrical power in which energ~ from the M~
effluent is utilized to increase system efficiency.
An important object of the present invention is to provide a method of generating electrical power, compris-ing introducins carbonaceous material and water to a gasifier, initiating and sustaininy the endotherrnic re-action of carbon and water thereby providiny a gasified stream containing carbon monoxide, hydrogen and nitrogen, passing the gasified stream and an ionizing ~eed material 10 to a burner and there contacting the gasified stream with preheated air, either ambient or enriched, to burn the gasi-fied stream thereby producing ionized combustion gas having a temperature greater than about 3600 F., accelerating the ionized combustion gas to a velocity greater than about 400 meters per second, passing the accelerated ionized combus-tion sas through an ~IIJD generator to generate DC power and thereafter through a diffuser to reduce the gas velocity, and passiny the gas from the diffuser in heat exhchange relationship with the gasifier to provide heat to sustain 20 the endothermic reaction of carbon and water.
Another object of the present invention is to provide a method of generating electrical power, comprising intro-ducing carbonaceous material and water to a gasifier, heat-ing the mixture of carbonaceous material and water to initiate and sustain the endothermic reaction of carbon and water thereby providing a sasified stream containing carbon monoxiae, hydrogen and nitrcgen, passing the gasified stream and an ionizing seed material and air from a preheater to a 1 1~7910 burner to burn the gasified stream thereby producing ioniz-ed combustion gas having a temperature greater than about 3600F., accelerating the ionized combustion gas to a velo-city greater than about 40~ meters per second, passing the accelerated ionized combustion gas through an MHD ~enerator to generate DC power and thereafter through a diffuser to reduce the gas velocity/ passing the gas from the diffuser to an afterburner to burn same, and passing the gas from the afterburner in heat exchange relationship ~ith the gasifier to provide heat to sustain the endothermic reac-tion of carbon and water and with the preheater to preheat the air prior to combustion with the gasified stream~
A still further obiect of the present invention is to provide a method of generating electrical power, comprising, introducing coal and water to a gasifier~ heating the :~.
mixture of coal and water to initiate and sustain the endo-thermic reaction of carbon and water thereby providing a gasified stream containing carbon monoxide, hydrogen and nitrogen, providing a compressor for compressing air and a preheater for preheating air, passing the gasified stream and an ionizing seed material and compressed preheated air having a temperature of up to about 3000F~ and a pressure of up to about 150 pounds per square inch to a burner to burn the gasified stream thereby producing ionized combus-tion gas havin~ a temperature in the range of from about 3600F, to about 6000F., accelerating the ionized combus-tion gas to a velocity in the range of from about 4ao meters per second to about 1100 meters per second, passing ~ 7 the accelerated ionized combustion gas through an MHD
generator to generate DC power and thereafter through a diffuser to reduce the gas velocity, passing the gas from the diffuser to an afterburner to burn same, and passing the gas from the afterburner in heat exchange relationship with the gasifier to provide heat to sustain the endothermic reaction of carbon and water and in heat exchange relation-ship with the preheater to provide heat for preheating air and extracting energy from the gas from the afterburner for energizing the compressor.
These and other objects of the present invention may more readily be understood by reference to the following specification taken in conjunction with the accompanying drawing, in which:
DESCRIPTION OF THE FIGURE
The single drawing Figure is a schematic diagram of a system for practicing the method of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawing, there is disclosed a system 50 which includes a steam gasifier 55 having connected thereto a water inlet 56 and a fuel inlet 57.
The fuel which is contemplated for use with the system 50 of the present invention includes any carbonaceous material such as coal, oil shale, tar sands, forest waste material, farm and municipal waste material, wood, lignite, peat, brown coal and the like. For simplicity sake, coal will be the assumed fuel. Although the system 50 is specifically designed to accommodate the endothermic reaction of carbon `` I 1S7910 and water producing carbon monoxide and hydrGgen, the system can accommodate up to about 20 volume percent oxygen supplied by air and still retain some advantages herein-after described. ~he preferred source of oxygen is water and water is ~referred to air. It is unders-tood, however, that all references to water in the foregoing description include air.
The steam gasifier 55 is the situs for the endothermic reaction resultiny in a mixture of gaseous carbon ~onoxide, 10 hydrogen, nitrogen and hydrogen sulfide, the hydrogen sul-fide resulting from the presence of sulfur may be removed from the system by techniques well known in the art. Ash produced as a result of the endothermic reaction settles by yravity and is removed throuyh a bottoms outlet 59 along with any coal slag. The gaseous product of carbon monoxide, hydrogen and nitrogen leaves the steam sasifier 55 through an outlet conduit 61. Heat to initiate and sustain the endo-thermic reaction in the steam gasifier 55 is provided by passing ~HD off gas, as will be explained through a heater 20 65 having an inlet 66 and an outlet 67, both connected to a conduit 70. Conduit 70 is schematically drawn as a single line and represents mechanism for transferring energ-y from the MHD off gas to several of the system 50 components. ~o specific order in energy transfer is intended by the draw-ing nor is the energy transfer limited to heat exchange.
The steam gasifier 55 is required to be cooled and there is included in the system 50 a water coolant supply 75 connected by an inlet 72 to a cooling coil 71 in heat ~ 1579~0 g exchange relationship with the gasifier, leaviny the coil 71 throuyh an outlet 76.
A burner 80 receives the gasifier product through the conduit 61 and there comingles same with hot cor~pressed air received from both an air compressor 90 and an air preheater 100. The air compressor 90 has an air inlet 91 and an outlet 98 in fluid communication with the air pre-heater 100. Energy is su~plied to the air compressor 90 by mechanism 95 suitably connected to the line 70 by inlet 96 and outlet 97. The air preheater 100 has a heater 105 havins an inlet 106 and an outlet 107, both also connected to the conduit 70. Air from the air preheater 100 exits through a conduit 101 in fluid communication with the burner 8C where the preheated air and the off gas from the steam gasifier 55 are combined and burned to produce combustion gas which leaves the burner 80 by a conduit 89. A cooling coil 81 having an inlet 82 connected to the outlet 76 of the coil 71 and an outlet conduit 83 serve to cool the burner 80 walls and to preserve the physical inteyrity thereof.
The cGmbustion yas from the burner 80 flows through the conduit 89 and through a noz21e (not shown) in which the gas is accelerated and then into an i1ED yenerator 110. The M~D senerator 110, as is well known in the art, is provided with means for establishing a magnetic field and opposed electrodes for collecting a current generated by the plasma flowing through the magnetic field. The power produced is DC power and is concucted from the M~D generator through 1 1S7gl~
- 10 ~
a line 119 to an inverter 120. The inverter 120 is an electrical devi.ce which concerts the DC power to the AC
power, the inefficiency of the inverter being represented as an energy dump 121.
MHD generator 110 is connected to a diffuser 130 which reduces the velocity of the ~ ID effluent and conducts same by a conduit 139 to an afterburner 140. ~oth the ~D
generator 110 and the diffuser 130 require cooliny and this is provided by means of cooling coils 111 and 131, respec-I0 tively each havins an inlet 112 and 132 and an outlet 113 and133, the outlet 133 being connected to the afterburner 140 to transfer the heat energy collected froM the gasifier 55, the burner 80, the generator 110 and the diffuser 130.
~ he afterburner 140 is provided with an air supply (not shown) and there burns the M~D effluent conveyed there-to through the conduit 139. mhe burned gas in the after-burner 140 is conducted by a conduit 141 to a stac~ 150 for exhaustion to the ~tmosphere or to cleanup equipment if necessary. Energy rrom the afterburner combustion gas is conducted by an outlet conduit 142 to a steam turbine 155 in which the gas is passed in heat exchange relationship with water to provide steam to drive the turbine, the output of which 156 is used to produce AC power from an AC
power generator 160. ~oth the steam turbine 155 and the AC
generator 160 have energy therefrom recycled respectively by lines 157 and 161 to the afterburner 1~0.
Enersy transfer mechanism 145 is positioned in the arterburner 140 with the inlet line 146 and outlet line 1.47 1 157~10 thereof being connected to the common conduit 70. The afterburner 140 is connected in energy exchange relationship with the steam gasifier 55, the air compressor 90 and the air preheater 100. Finally, a portion of the energy produced in the system 50 is lost as cooling losses in the afterburner 140 and elsewhere and is represented by a dump 144. An auxiliary power source 165 provides additional energy to the system 150 through a line 166, schematically joining the system 150 byan electrical connector 166 to the afterburner 140.
An example is hereinafter set forth wherein calculated efficiency is 43~ based on an input of 236.7 megawatts of chemical energy per hour (hereinafter ~c) and having a net output of 123.6 megawatts of electrical energy per hour (hereinafter MWe). Water is introduced into the system S0 through the line 56 at the flow rate of 46,893 pounds per hour at an ambient temperature of about 80F. and M.ontana coal (analysis hereinafter set forth) is introduced into the steam gasifier 55 at a flow rate of 109,847 pounds per hour, the coal having a heat value of 8,920 btu per pound and 286.7 MWc. In order to initiate and sustain the endo-thermic reaction heretofore discussed in the steam gasifier 55, energy in the amount of 210.1 megawatts thermal per hour (hereinafter MWt) must be added to the gasifier 55 by the heater 65. The gases leaving the steam gasifier 55 through the outlet conduit 61 leave at a flow rate of 146,186 pounds per hour at a temperature of 1880F. having an enthalpy of 1,273 btu per pound, and 54.5 ~t and 379.3 ,~c.
~ 1~79t~
The hydrogen sulfide and ash leaving the steam gasifier 55 respectively through lines 58 and 59 have flow rates of 989 pounds per hour and 9,565 pounds per hour, respectively, both at a temperature of 1880F. and at enthalpies of 450 btu per pound and 324 btu per pound, respectively. The combined streams 58 a~d 59 also have a energy level of 2.8 MWc and 1.0 MWt.
Using Montana coal as basis for calculation, and using a 1 pound sample: carbon content is 0.5211; hydrogen content is 0.0601; sulfur content is 0.0086; nitrogen content is 0.0080; oxygen content is 0.3151, and the ash content is 0.0871. The steam gasification of the above sample of coal on a per pound basis requires 0.379 pounds of oxygen supplied as 0.427 pounds of water per pound of coal. The product from the gasifier 55 leaving through line 61 to the burner 80 includes (on a per pound coal basis) 1.216 pounds carbon monoxide, 0.107 pounds hydrogen gas, 0.009 pounds hydrogen sulfide gas, 0.008 pounds nitrogen gas and 0.087 pounds ash. Both the ash and the hydrogen sulfide are taken out as previously indicated leaving the carbon monoxide, hydrogen and nitrogen to be conveyed to the burner 80.
As indicated, the off gas from the steam gasifier 55 flows through line 61 to the burner 80 at a flow rate of 146,186 pounds per hour at a temperature of 1880F. and has energy of 54.5 MWt and 379.3 ~c, and potassium carbonate or potassium sulfate seed is introduced to the burner through line 86 at a flow rate of 17,700 pounds per hour.
The burner 80 also receives in addition to the ~ 1S79~
aforementioned gasifier off product preheated air from the air preheater 100. Energy at the rate of 22.3 MWt ls used by the air compressor 90 to compress the air therein to 70 psi at a temperature of about 495F. The flow rate of air leaving the compressor 90 through the line 9~ is 754,537 pounds per hour at the aforementioned temperature and pressure, the air having an energy of 22.3 l~t. Energy is added to the air preheater 100 at the rate of 156.1 ~Wt from the afterburner 140 and the air leaving the preheater is at the same flow rate as the air in, that is, 754,537 pounds per hour and at the same pressure of about 70 psi but the temperature at.the outlet is 3,000F. and at an energy of 17~.4 MWt. In the burner 80 the product from the gasifer 55 is burned with the preheated air and combustion gas leaves the burner 80 through line 89 at a flow rate of 918,423 pounds per hour at a temperature of about 5,315F., the off gases having an energy of about 555 .~Wt. The burner 80 like other components in the system 50 require cooling coils to maintain the structual integrity thereof, and therefore, energy in the amount of 3.06 ~t is removed by coolant flow through the cooling coils 81.
The combustion gas from the burner 80 is accelerated through a nozzle (not shown) and enters the MHD generator 110 at a velocity of up to 1, loo meters per second thereby generating DC power at the rate of about 94.4 ~lWe leaving the generator 110 as indicated through the conductor 119 to the inverter 120 for conversion to AC power at the rate of 92.5 MWe, the difference of 1.9 MWt being lost due to 1 1579~0 the inefficie~cy of the inverter and being illustrated at 121 in the drawing. The MHD generator 110 as is true with the other components in the system requires cooling, and therefore, energy at the rate of 31.9 ~Wt is removed by coolant flow through the coils 111.
Off gas from the generator 110 flows through the diffuser 130, whereby the velocity of the MHD effluent leaving the diffuser is about 100 meters per second at a rate of about 918,423 pounds per hour. The temperature of the gas leaving the diffuser 130 is 4,301F having an energy of 398.8 MWt, and the energy leaving the diffu-ser via cooling coil 131 is 29.9 MWt.
The MHD effluent leaving the diffuser 130 is burned in the afterburner 140 and a portion of the energy is recycled to the steam gasifier 55, the air compressor 90 and the preheater 100 to improve the efficiency of the system and to conserve fuel usually necessary to operate the air preheater, the air compressor and provide the energy necessary to initiate and sustain the endothermic reaction in the steam gasifier. Gas from the afterburner 140 leaves through line 141 to the stack 150 at a tempera-ture of about 250F. and an energy of about 20 MWt.
Additionally total cooling losses from the system indicated at 144 are at a level of about 143.1 MWt taking into account cooling losses from the steam gasifier 55, burner 80,the MHD generator 110, the diffuser 130 and the afterburner 140.
The afterburner itself supplies an additional 26.6 MWt to the combustion of gases therein and a portion of this l 157910 energy in addition to the energy from the MHD effluent is transmitted via line 142 to the steam turblne 155 and hence to the AC generator 160 for the production of AC power at the rate of 41.2 MWe. Both the AC generator and the steam turbine recycle 9.7 MWe energy to the afterburner 140.
An energy balance for the afterburner 140 is:
Energy (MHD effluent)398.8 Ml~t Energy (cooling coils) 151.6 MWt Energy (afterburner)26.6 MWt Energy (Auxiliary power added) 10.1 MWt Energy In =587.1 MWt Energy (air compressor) 22.3 MWt Energy (air preheater) 156.1 MWt Energy (steam gasifier) 210.1 MWt Energy (stack gases) 20.0 MWt Energy (Net) (steam turbine &
AC generator) 41.2 MWt Energy (cooling losses) 137.4 MWt Energy Out = 587.1 ~t The burner 80 and the ~HD generator 110 are the core of the system 50. Although the pressure of the gases in the preferred embodiment is about 70 psi, the burner 80 may operate within pressure ranges of from about 20 psi to about 150 psi. If pressures are less than about 20 psi, the power produced in the MHD generator 110 decreases to an unacceptable level. The power generated in the MHD
l 1~791~
generator 110 is related to the mass flow rate through the generator and if pressures are less than about 20 psi, the gas density is sufficiently low that the conductivitv of the gas decreases as well as the mass flow rate, both resulting in decreased power out of the MHD generator.
Pressures in excess of about 150 psi are undesirable because the equipment necessary to accommodate these pressures is more sophisticated and expensive, that is pressure vessel technology is required to handle pressures in excess of about 150 psi and this is unnecessary and therefore an undesirable expense.
Although the preferred embodiment illustrated tempera-ture of the combustion gas from the burner 80 of 5,315F., the system 50 will accommodate temperatures for the combus-tion gas from the burner 80 within a range of from about 3600F. to about 6000F. ~emperatures in excess of 6000F require more sophisticated metal technology to accommodate the high temperature while temperatures less than about 3600F. do not provide good electrical conducting plasma. It is realized, as heretofore stated, that higher gas temperatures are more desirable from an electrical conductivity view point and a power output view, but nevertheless the ranges aforesaid should be maintained.
As is well understood by those skilled in the art, temperature and pressure parameters of the burner 80 are influenced by the temperatures and pressures of the output from both the steam gasifier 55 and the air preheater 100.
~levertheless, each of these componen~s can be operated within said temperature and pressure ranges but a lower temperature in the steam gasifier 55 will require a higher temperature in the air preheater 100 and so on. The steam gasifier 55 may be operated in the temperature range of from about 1300F. to about 2500F. Temperatures less than about 1300F. do not produce a sufficient gasification reaction without a catalyst and therefore are not preferred. The temperature of about 2500F. is the upper limit because of material handling problems.
The air compressor 65 generally will put out air at a temperature of about 500F. for a pressure of 70 psi. Both the output temperature and the output pressure of air from the air compressor 65 are interrelated and are generally not individually variable. The air preheater may be operat-ed to produce preheated air having a temperature in the range of from about 500F. to about 3000F. Preferably, the higher temperature is utilized in order to require less eneryy from the burner 80. Where the low temperatures of 500F. is utilized, then the steam gasifier 55 must be ~0 operated at a higher temperature to accommodate for the low preheat temperature. As before stated, there is an interrelationship between the temperature and pressure of the output from the air preheater 100 and the temperature of output from the steam gasifier 55 in order to achieve the desired temperature output from the burner 30.
The seed isan alkali metal salt and preferably potassium sulfate or potassium carbonate and the flow rate of 17,700 pounds per hour is selected to satisfy the 1 1S7glO
parameters of the preferred embodiment, but it is under-stood that the seed flow rate may be varied within a wide range of parameters necessary to maintain adequate seeding and conductivity of the gas through the MHD generator 110.
Because ash is removed from the steam gasifier 55, the ash is not present in the combustion gas produced in the burner 80 and therefore seed recovery is facilitated and this is a ma~or advantage of the present invention. The combustion gas from the burner 80 consists primarily of carbon dioxide and water with some carbon monoxide being present along with nitrogen. There is substantially no ash nor is there any substantial quantity of hydrogen sulfide, this preferably having been separated in the steam gasifier 55.
The MHD generator 110 and the diffuser 130 are usually considered as a single unit and the temperature and pressure ranges aforesaid for the burner ~0 hold true for the MHD
generator and the diffuser. The MHD generator 110 may be operated in conjunction with the nozzle (not shown) to accommodate plasma velocities in the range of from about 20 0.4 to about 1.1 mach or from about 400 to about llOOmeters per second. The temperature of the gas leaving the diffuser 130 is about 1000 less than the gas entering the MHD generator 110 or in the preferred embodi~ent, the temperature of the gas in is about 5,315F. and the gas out of the diffuser are 4,301F. With respect to the velocity ranges, velocities of the plasma less than about 400 meters per second resul-t in an unacceptable decrease in the power output since the power output of the generator ~ 157910 -- lg --depends on the mass passing through the generator and the mass depends on the velocity and the gas density. Gas velocities greater than about 1100 meters per second result in instabilities in the plasma which are undesirable and therefore the upper limit is set near 1 mach.
The temperatures and pressures acceptable in the after-burner 140 are the same as those acceptable for the burner 80 and for the same reasons.
There has been provided a method for generating electrical power utilizing a steam gasifier and MHD genera-tor which utilizes energy from the MHD effluent or off gas to maintain the endothermic reaction in the steam gasifier, operate the air preheater and the air compressor. The overall efficiency of the present method is greater than heretofore reported in the literature due to the recycle of energy through the MI~D generator via the gasifier, air preheater and compressor. Use of endothermic coal gasifi-cation reaction with water or steam rather than oxygen is central to the inventive method, although up to 20 volume percent of oxygen can be accommodated without losing all the advantages of the present system. Another significant advantage of the inventive method is that it is unnecessary to dry fuel or coal prior to introduction to the system, thereby saving energy. Additionally, high moisture fuels such as forest, farm and municipal waste, wood, lignite, peat and brown coal are economical to use in the inventive system since drying is unnecessary. Other fuels such as oil shale and tar sands or mi~tures of any of the above 1 1~79~0 named fuels may be used in the system without ~etractiny from any of the advantayes thereof.
Because the coal slag is removed in the yasifier and is never transmitted to the M~D generator, separation of the seed material from coal slag or ash is not requirea and represents a significant saving over prior systems.
While for illustration purposes a steam gasifier has been illustrated herein, it should be understood that other gasifier inputs may include well known material such as water, carbon dioxide or air.
~ hile there has been described what at present is consiaered to be the preferred embodiment of the present invention, it will be understood that various modifications and alterations may be made therein without departing from the true scope of the invention, and it is intended to cover in the claims appended hereto all such modifications and alterations.
ME:THOD OF GENER~TING ELECTRICITY USI~G AN
ENDOTHE~MIC COAL GASIFIER AND MHD GE21ERATOR
BACKGROUND OF THE INVENTION
The development of the magnetohydrodynamic (MHD) generator has been considered important because of several advanta~es. These include a low capital cost, greater efficiency of heat conversion to electrical energy and rapid start-up. The development of the MHD generator has been hampered by several problems, especially in the case of coal combustion. Among these problems are the effect of ash on the process equipment, the removal of the ash and separation of the ash or coal slag from khe seed. Low combustion temperatures which require the necessity of pre-heating air to the burner and the low overall MHD efficiency due to the high energy content of the effl-lent gases from the MHD generator pose additional problems.
In general terms, MHD generators produce electrical power by movement of electr-ically conductive fluid relative to a magnetlc field. The fluid employed is usually an electrically conductive gas from a high temperature, high pressure source. From the source, the fluid flows through the generator and, by virtue of its movement relative to the magnetic field, induces an electromotive force between opposed electrodes in the generator. The gas may exhaust to a sink which may simply be the atmosphere; or, in a more sophisticated system, the gas may exhaust to a reco-very system including pumping mechanism for returning the gas to the source.
~everal different gases may be used; the gas may be products of combustion, or may comprise inert gases such as helium or argon. In open systems, such as those in which the gases are not recycled after passing through the power plant, products of combustion are normally used. In closed systems, in which the gases are recycled, it is feasible to use relatively expensive gases, such as helium and argon.
To promote electrical conductivity, the gases are heated to a high temperature; conductivity is also increased by the addition to the gases of a substance that ionizes readily at the operating temperatures of the generator. Regardless of the gas used, the gas includes a mixture of electrons, positive ions and neutral atoms which, for convenience, is usually termed "plasma".
The temperature of the plasma is highly significant, not only to the overall efficiency of the systen~ but also to the design of the MHD generator. With a higher temperature available at the inlet of the generator, a larger isentropic drop can be developed as the plasma expands through the generator, resulting in an improved plant efficiency.
` ` 1 157910 Because the electrical conductivity of the plasma increases as the temperature increases, it is possible to generate a given amount of power in a relatively smaller generator and employ a smaller magnetic field than would otherwise be - possible with employment of increased temperatures. The increased efficiency of the MHD system, considerably above that of conventional steam turbine plants, coupled with the absence of hot moving parts in the generator suggest that in time MHD power plants will replace or substantially sup-plant power generating systems of conventional design.
Some of the problems endemic to MHD systems, even after the substantial amount of development work over the past several years includes the loss of high energy gas from the MHD generator as well as the necessity to preheat air in order to obtain the requisite high temperatures at the generator inlet and to dry and preheat the fuel, particularly where coal is employed.
~epresentative literature relating to MHD generating systems includes U.S. Patent No. 3,414,744 issued December 3, 1968 to Petrick for Magnetohydrodynamic Generator which discloses the use of an r~HD generator using Na~ coolant from a nuclear reactor.
U.S. Patent No. 3,531,665 issued September 29, 1970 to Rosa for Coal Preheating System For Magnetohydrodynamic Devices which discloses mechanism for preheating pulverized coal with MHD off gas.
U.S. Patent No. 3,720,850 issued March 13, 1973 to T~ay for Magnetohydrodynamic Power System With Semi-Closed ` 1 157910 Cycle shows the recycling of MHD off gases to the inlet side of the MHD generator.
U.S. Patent No. 3,873,845 issued March 25, 1975 to Osthaus for Method Of Producing Electric Energy Including Coal Gasification discloses a process and system for gasi-fying coal dust with air heated to 1500C., the combustion gas therefrom being cooled to 150C. thereby producing high pressure steam for producing electricity.
U.S. Patent No. 3,895,243 issued July 15, 1975 to Amend et al. for Method And Means Of Generating Power From Fossil Fuels With A Combined Plasma And Liquid-Metal MHD
Cycle discloses a process for utili~ing the waste heat from a fossil fuel MHD generator to heat a llquid-metal MHD
generator. Air is preheated ~y heat exchange with the walls of the combustion chamber for the MHD generator.
U.S. Patent No. 4,064,222 issued December 23, 1977 to Bretz for Nitrogen Fixation And Molecular Magneto Hydro-dynamic Generation Using A Coal Gasification Gas Stream discloses a coal gasifier using coal and oxygen to produce off gas which is burned wi~h air and fed to a MHD generator followed by adiabat~c expans~on to fix the nitrogen oxides.
U.S. Patent ~o. 4,107,557 issued August 15, 1978 to Shepard for Sulfur-Fueled Magnetohydrodynamic Power Genera-tion discloses a closed cycle MHD generator using sulfur and oxygen to produce a flame temperature of greater than 8000F. to the MHD generator.
SUMMARY OF THE INVENTION
This invention relates to a method and system of generating electrical power in which energ~ from the M~
effluent is utilized to increase system efficiency.
An important object of the present invention is to provide a method of generating electrical power, compris-ing introducins carbonaceous material and water to a gasifier, initiating and sustaininy the endotherrnic re-action of carbon and water thereby providiny a gasified stream containing carbon monoxide, hydrogen and nitrogen, passing the gasified stream and an ionizing ~eed material 10 to a burner and there contacting the gasified stream with preheated air, either ambient or enriched, to burn the gasi-fied stream thereby producing ionized combustion gas having a temperature greater than about 3600 F., accelerating the ionized combustion gas to a velocity greater than about 400 meters per second, passing the accelerated ionized combus-tion sas through an ~IIJD generator to generate DC power and thereafter through a diffuser to reduce the gas velocity, and passiny the gas from the diffuser in heat exhchange relationship with the gasifier to provide heat to sustain 20 the endothermic reaction of carbon and water.
Another object of the present invention is to provide a method of generating electrical power, comprising intro-ducing carbonaceous material and water to a gasifier, heat-ing the mixture of carbonaceous material and water to initiate and sustain the endothermic reaction of carbon and water thereby providing a sasified stream containing carbon monoxiae, hydrogen and nitrcgen, passing the gasified stream and an ionizing seed material and air from a preheater to a 1 1~7910 burner to burn the gasified stream thereby producing ioniz-ed combustion gas having a temperature greater than about 3600F., accelerating the ionized combustion gas to a velo-city greater than about 40~ meters per second, passing the accelerated ionized combustion gas through an MHD ~enerator to generate DC power and thereafter through a diffuser to reduce the gas velocity/ passing the gas from the diffuser to an afterburner to burn same, and passing the gas from the afterburner in heat exchange relationship ~ith the gasifier to provide heat to sustain the endothermic reac-tion of carbon and water and with the preheater to preheat the air prior to combustion with the gasified stream~
A still further obiect of the present invention is to provide a method of generating electrical power, comprising, introducing coal and water to a gasifier~ heating the :~.
mixture of coal and water to initiate and sustain the endo-thermic reaction of carbon and water thereby providing a gasified stream containing carbon monoxide, hydrogen and nitrogen, providing a compressor for compressing air and a preheater for preheating air, passing the gasified stream and an ionizing seed material and compressed preheated air having a temperature of up to about 3000F~ and a pressure of up to about 150 pounds per square inch to a burner to burn the gasified stream thereby producing ionized combus-tion gas havin~ a temperature in the range of from about 3600F, to about 6000F., accelerating the ionized combus-tion gas to a velocity in the range of from about 4ao meters per second to about 1100 meters per second, passing ~ 7 the accelerated ionized combustion gas through an MHD
generator to generate DC power and thereafter through a diffuser to reduce the gas velocity, passing the gas from the diffuser to an afterburner to burn same, and passing the gas from the afterburner in heat exchange relationship with the gasifier to provide heat to sustain the endothermic reaction of carbon and water and in heat exchange relation-ship with the preheater to provide heat for preheating air and extracting energy from the gas from the afterburner for energizing the compressor.
These and other objects of the present invention may more readily be understood by reference to the following specification taken in conjunction with the accompanying drawing, in which:
DESCRIPTION OF THE FIGURE
The single drawing Figure is a schematic diagram of a system for practicing the method of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawing, there is disclosed a system 50 which includes a steam gasifier 55 having connected thereto a water inlet 56 and a fuel inlet 57.
The fuel which is contemplated for use with the system 50 of the present invention includes any carbonaceous material such as coal, oil shale, tar sands, forest waste material, farm and municipal waste material, wood, lignite, peat, brown coal and the like. For simplicity sake, coal will be the assumed fuel. Although the system 50 is specifically designed to accommodate the endothermic reaction of carbon `` I 1S7910 and water producing carbon monoxide and hydrGgen, the system can accommodate up to about 20 volume percent oxygen supplied by air and still retain some advantages herein-after described. ~he preferred source of oxygen is water and water is ~referred to air. It is unders-tood, however, that all references to water in the foregoing description include air.
The steam gasifier 55 is the situs for the endothermic reaction resultiny in a mixture of gaseous carbon ~onoxide, 10 hydrogen, nitrogen and hydrogen sulfide, the hydrogen sul-fide resulting from the presence of sulfur may be removed from the system by techniques well known in the art. Ash produced as a result of the endothermic reaction settles by yravity and is removed throuyh a bottoms outlet 59 along with any coal slag. The gaseous product of carbon monoxide, hydrogen and nitrogen leaves the steam sasifier 55 through an outlet conduit 61. Heat to initiate and sustain the endo-thermic reaction in the steam gasifier 55 is provided by passing ~HD off gas, as will be explained through a heater 20 65 having an inlet 66 and an outlet 67, both connected to a conduit 70. Conduit 70 is schematically drawn as a single line and represents mechanism for transferring energ-y from the MHD off gas to several of the system 50 components. ~o specific order in energy transfer is intended by the draw-ing nor is the energy transfer limited to heat exchange.
The steam gasifier 55 is required to be cooled and there is included in the system 50 a water coolant supply 75 connected by an inlet 72 to a cooling coil 71 in heat ~ 1579~0 g exchange relationship with the gasifier, leaviny the coil 71 throuyh an outlet 76.
A burner 80 receives the gasifier product through the conduit 61 and there comingles same with hot cor~pressed air received from both an air compressor 90 and an air preheater 100. The air compressor 90 has an air inlet 91 and an outlet 98 in fluid communication with the air pre-heater 100. Energy is su~plied to the air compressor 90 by mechanism 95 suitably connected to the line 70 by inlet 96 and outlet 97. The air preheater 100 has a heater 105 havins an inlet 106 and an outlet 107, both also connected to the conduit 70. Air from the air preheater 100 exits through a conduit 101 in fluid communication with the burner 8C where the preheated air and the off gas from the steam gasifier 55 are combined and burned to produce combustion gas which leaves the burner 80 by a conduit 89. A cooling coil 81 having an inlet 82 connected to the outlet 76 of the coil 71 and an outlet conduit 83 serve to cool the burner 80 walls and to preserve the physical inteyrity thereof.
The cGmbustion yas from the burner 80 flows through the conduit 89 and through a noz21e (not shown) in which the gas is accelerated and then into an i1ED yenerator 110. The M~D senerator 110, as is well known in the art, is provided with means for establishing a magnetic field and opposed electrodes for collecting a current generated by the plasma flowing through the magnetic field. The power produced is DC power and is concucted from the M~D generator through 1 1S7gl~
- 10 ~
a line 119 to an inverter 120. The inverter 120 is an electrical devi.ce which concerts the DC power to the AC
power, the inefficiency of the inverter being represented as an energy dump 121.
MHD generator 110 is connected to a diffuser 130 which reduces the velocity of the ~ ID effluent and conducts same by a conduit 139 to an afterburner 140. ~oth the ~D
generator 110 and the diffuser 130 require cooliny and this is provided by means of cooling coils 111 and 131, respec-I0 tively each havins an inlet 112 and 132 and an outlet 113 and133, the outlet 133 being connected to the afterburner 140 to transfer the heat energy collected froM the gasifier 55, the burner 80, the generator 110 and the diffuser 130.
~ he afterburner 140 is provided with an air supply (not shown) and there burns the M~D effluent conveyed there-to through the conduit 139. mhe burned gas in the after-burner 140 is conducted by a conduit 141 to a stac~ 150 for exhaustion to the ~tmosphere or to cleanup equipment if necessary. Energy rrom the afterburner combustion gas is conducted by an outlet conduit 142 to a steam turbine 155 in which the gas is passed in heat exchange relationship with water to provide steam to drive the turbine, the output of which 156 is used to produce AC power from an AC
power generator 160. ~oth the steam turbine 155 and the AC
generator 160 have energy therefrom recycled respectively by lines 157 and 161 to the afterburner 1~0.
Enersy transfer mechanism 145 is positioned in the arterburner 140 with the inlet line 146 and outlet line 1.47 1 157~10 thereof being connected to the common conduit 70. The afterburner 140 is connected in energy exchange relationship with the steam gasifier 55, the air compressor 90 and the air preheater 100. Finally, a portion of the energy produced in the system 50 is lost as cooling losses in the afterburner 140 and elsewhere and is represented by a dump 144. An auxiliary power source 165 provides additional energy to the system 150 through a line 166, schematically joining the system 150 byan electrical connector 166 to the afterburner 140.
An example is hereinafter set forth wherein calculated efficiency is 43~ based on an input of 236.7 megawatts of chemical energy per hour (hereinafter ~c) and having a net output of 123.6 megawatts of electrical energy per hour (hereinafter MWe). Water is introduced into the system S0 through the line 56 at the flow rate of 46,893 pounds per hour at an ambient temperature of about 80F. and M.ontana coal (analysis hereinafter set forth) is introduced into the steam gasifier 55 at a flow rate of 109,847 pounds per hour, the coal having a heat value of 8,920 btu per pound and 286.7 MWc. In order to initiate and sustain the endo-thermic reaction heretofore discussed in the steam gasifier 55, energy in the amount of 210.1 megawatts thermal per hour (hereinafter MWt) must be added to the gasifier 55 by the heater 65. The gases leaving the steam gasifier 55 through the outlet conduit 61 leave at a flow rate of 146,186 pounds per hour at a temperature of 1880F. having an enthalpy of 1,273 btu per pound, and 54.5 ~t and 379.3 ,~c.
~ 1~79t~
The hydrogen sulfide and ash leaving the steam gasifier 55 respectively through lines 58 and 59 have flow rates of 989 pounds per hour and 9,565 pounds per hour, respectively, both at a temperature of 1880F. and at enthalpies of 450 btu per pound and 324 btu per pound, respectively. The combined streams 58 a~d 59 also have a energy level of 2.8 MWc and 1.0 MWt.
Using Montana coal as basis for calculation, and using a 1 pound sample: carbon content is 0.5211; hydrogen content is 0.0601; sulfur content is 0.0086; nitrogen content is 0.0080; oxygen content is 0.3151, and the ash content is 0.0871. The steam gasification of the above sample of coal on a per pound basis requires 0.379 pounds of oxygen supplied as 0.427 pounds of water per pound of coal. The product from the gasifier 55 leaving through line 61 to the burner 80 includes (on a per pound coal basis) 1.216 pounds carbon monoxide, 0.107 pounds hydrogen gas, 0.009 pounds hydrogen sulfide gas, 0.008 pounds nitrogen gas and 0.087 pounds ash. Both the ash and the hydrogen sulfide are taken out as previously indicated leaving the carbon monoxide, hydrogen and nitrogen to be conveyed to the burner 80.
As indicated, the off gas from the steam gasifier 55 flows through line 61 to the burner 80 at a flow rate of 146,186 pounds per hour at a temperature of 1880F. and has energy of 54.5 MWt and 379.3 ~c, and potassium carbonate or potassium sulfate seed is introduced to the burner through line 86 at a flow rate of 17,700 pounds per hour.
The burner 80 also receives in addition to the ~ 1S79~
aforementioned gasifier off product preheated air from the air preheater 100. Energy at the rate of 22.3 MWt ls used by the air compressor 90 to compress the air therein to 70 psi at a temperature of about 495F. The flow rate of air leaving the compressor 90 through the line 9~ is 754,537 pounds per hour at the aforementioned temperature and pressure, the air having an energy of 22.3 l~t. Energy is added to the air preheater 100 at the rate of 156.1 ~Wt from the afterburner 140 and the air leaving the preheater is at the same flow rate as the air in, that is, 754,537 pounds per hour and at the same pressure of about 70 psi but the temperature at.the outlet is 3,000F. and at an energy of 17~.4 MWt. In the burner 80 the product from the gasifer 55 is burned with the preheated air and combustion gas leaves the burner 80 through line 89 at a flow rate of 918,423 pounds per hour at a temperature of about 5,315F., the off gases having an energy of about 555 .~Wt. The burner 80 like other components in the system 50 require cooling coils to maintain the structual integrity thereof, and therefore, energy in the amount of 3.06 ~t is removed by coolant flow through the cooling coils 81.
The combustion gas from the burner 80 is accelerated through a nozzle (not shown) and enters the MHD generator 110 at a velocity of up to 1, loo meters per second thereby generating DC power at the rate of about 94.4 ~lWe leaving the generator 110 as indicated through the conductor 119 to the inverter 120 for conversion to AC power at the rate of 92.5 MWe, the difference of 1.9 MWt being lost due to 1 1579~0 the inefficie~cy of the inverter and being illustrated at 121 in the drawing. The MHD generator 110 as is true with the other components in the system requires cooling, and therefore, energy at the rate of 31.9 ~Wt is removed by coolant flow through the coils 111.
Off gas from the generator 110 flows through the diffuser 130, whereby the velocity of the MHD effluent leaving the diffuser is about 100 meters per second at a rate of about 918,423 pounds per hour. The temperature of the gas leaving the diffuser 130 is 4,301F having an energy of 398.8 MWt, and the energy leaving the diffu-ser via cooling coil 131 is 29.9 MWt.
The MHD effluent leaving the diffuser 130 is burned in the afterburner 140 and a portion of the energy is recycled to the steam gasifier 55, the air compressor 90 and the preheater 100 to improve the efficiency of the system and to conserve fuel usually necessary to operate the air preheater, the air compressor and provide the energy necessary to initiate and sustain the endothermic reaction in the steam gasifier. Gas from the afterburner 140 leaves through line 141 to the stack 150 at a tempera-ture of about 250F. and an energy of about 20 MWt.
Additionally total cooling losses from the system indicated at 144 are at a level of about 143.1 MWt taking into account cooling losses from the steam gasifier 55, burner 80,the MHD generator 110, the diffuser 130 and the afterburner 140.
The afterburner itself supplies an additional 26.6 MWt to the combustion of gases therein and a portion of this l 157910 energy in addition to the energy from the MHD effluent is transmitted via line 142 to the steam turblne 155 and hence to the AC generator 160 for the production of AC power at the rate of 41.2 MWe. Both the AC generator and the steam turbine recycle 9.7 MWe energy to the afterburner 140.
An energy balance for the afterburner 140 is:
Energy (MHD effluent)398.8 Ml~t Energy (cooling coils) 151.6 MWt Energy (afterburner)26.6 MWt Energy (Auxiliary power added) 10.1 MWt Energy In =587.1 MWt Energy (air compressor) 22.3 MWt Energy (air preheater) 156.1 MWt Energy (steam gasifier) 210.1 MWt Energy (stack gases) 20.0 MWt Energy (Net) (steam turbine &
AC generator) 41.2 MWt Energy (cooling losses) 137.4 MWt Energy Out = 587.1 ~t The burner 80 and the ~HD generator 110 are the core of the system 50. Although the pressure of the gases in the preferred embodiment is about 70 psi, the burner 80 may operate within pressure ranges of from about 20 psi to about 150 psi. If pressures are less than about 20 psi, the power produced in the MHD generator 110 decreases to an unacceptable level. The power generated in the MHD
l 1~791~
generator 110 is related to the mass flow rate through the generator and if pressures are less than about 20 psi, the gas density is sufficiently low that the conductivitv of the gas decreases as well as the mass flow rate, both resulting in decreased power out of the MHD generator.
Pressures in excess of about 150 psi are undesirable because the equipment necessary to accommodate these pressures is more sophisticated and expensive, that is pressure vessel technology is required to handle pressures in excess of about 150 psi and this is unnecessary and therefore an undesirable expense.
Although the preferred embodiment illustrated tempera-ture of the combustion gas from the burner 80 of 5,315F., the system 50 will accommodate temperatures for the combus-tion gas from the burner 80 within a range of from about 3600F. to about 6000F. ~emperatures in excess of 6000F require more sophisticated metal technology to accommodate the high temperature while temperatures less than about 3600F. do not provide good electrical conducting plasma. It is realized, as heretofore stated, that higher gas temperatures are more desirable from an electrical conductivity view point and a power output view, but nevertheless the ranges aforesaid should be maintained.
As is well understood by those skilled in the art, temperature and pressure parameters of the burner 80 are influenced by the temperatures and pressures of the output from both the steam gasifier 55 and the air preheater 100.
~levertheless, each of these componen~s can be operated within said temperature and pressure ranges but a lower temperature in the steam gasifier 55 will require a higher temperature in the air preheater 100 and so on. The steam gasifier 55 may be operated in the temperature range of from about 1300F. to about 2500F. Temperatures less than about 1300F. do not produce a sufficient gasification reaction without a catalyst and therefore are not preferred. The temperature of about 2500F. is the upper limit because of material handling problems.
The air compressor 65 generally will put out air at a temperature of about 500F. for a pressure of 70 psi. Both the output temperature and the output pressure of air from the air compressor 65 are interrelated and are generally not individually variable. The air preheater may be operat-ed to produce preheated air having a temperature in the range of from about 500F. to about 3000F. Preferably, the higher temperature is utilized in order to require less eneryy from the burner 80. Where the low temperatures of 500F. is utilized, then the steam gasifier 55 must be ~0 operated at a higher temperature to accommodate for the low preheat temperature. As before stated, there is an interrelationship between the temperature and pressure of the output from the air preheater 100 and the temperature of output from the steam gasifier 55 in order to achieve the desired temperature output from the burner 30.
The seed isan alkali metal salt and preferably potassium sulfate or potassium carbonate and the flow rate of 17,700 pounds per hour is selected to satisfy the 1 1S7glO
parameters of the preferred embodiment, but it is under-stood that the seed flow rate may be varied within a wide range of parameters necessary to maintain adequate seeding and conductivity of the gas through the MHD generator 110.
Because ash is removed from the steam gasifier 55, the ash is not present in the combustion gas produced in the burner 80 and therefore seed recovery is facilitated and this is a ma~or advantage of the present invention. The combustion gas from the burner 80 consists primarily of carbon dioxide and water with some carbon monoxide being present along with nitrogen. There is substantially no ash nor is there any substantial quantity of hydrogen sulfide, this preferably having been separated in the steam gasifier 55.
The MHD generator 110 and the diffuser 130 are usually considered as a single unit and the temperature and pressure ranges aforesaid for the burner ~0 hold true for the MHD
generator and the diffuser. The MHD generator 110 may be operated in conjunction with the nozzle (not shown) to accommodate plasma velocities in the range of from about 20 0.4 to about 1.1 mach or from about 400 to about llOOmeters per second. The temperature of the gas leaving the diffuser 130 is about 1000 less than the gas entering the MHD generator 110 or in the preferred embodi~ent, the temperature of the gas in is about 5,315F. and the gas out of the diffuser are 4,301F. With respect to the velocity ranges, velocities of the plasma less than about 400 meters per second resul-t in an unacceptable decrease in the power output since the power output of the generator ~ 157910 -- lg --depends on the mass passing through the generator and the mass depends on the velocity and the gas density. Gas velocities greater than about 1100 meters per second result in instabilities in the plasma which are undesirable and therefore the upper limit is set near 1 mach.
The temperatures and pressures acceptable in the after-burner 140 are the same as those acceptable for the burner 80 and for the same reasons.
There has been provided a method for generating electrical power utilizing a steam gasifier and MHD genera-tor which utilizes energy from the MHD effluent or off gas to maintain the endothermic reaction in the steam gasifier, operate the air preheater and the air compressor. The overall efficiency of the present method is greater than heretofore reported in the literature due to the recycle of energy through the MI~D generator via the gasifier, air preheater and compressor. Use of endothermic coal gasifi-cation reaction with water or steam rather than oxygen is central to the inventive method, although up to 20 volume percent of oxygen can be accommodated without losing all the advantages of the present system. Another significant advantage of the inventive method is that it is unnecessary to dry fuel or coal prior to introduction to the system, thereby saving energy. Additionally, high moisture fuels such as forest, farm and municipal waste, wood, lignite, peat and brown coal are economical to use in the inventive system since drying is unnecessary. Other fuels such as oil shale and tar sands or mi~tures of any of the above 1 1~79~0 named fuels may be used in the system without ~etractiny from any of the advantayes thereof.
Because the coal slag is removed in the yasifier and is never transmitted to the M~D generator, separation of the seed material from coal slag or ash is not requirea and represents a significant saving over prior systems.
While for illustration purposes a steam gasifier has been illustrated herein, it should be understood that other gasifier inputs may include well known material such as water, carbon dioxide or air.
~ hile there has been described what at present is consiaered to be the preferred embodiment of the present invention, it will be understood that various modifications and alterations may be made therein without departing from the true scope of the invention, and it is intended to cover in the claims appended hereto all such modifications and alterations.
Claims (18)
1. A method of generating electrical power, comprising:
introducing carbonaceous material and water to a gasifier, initiating and sustaining the endothermic reaction of carbon and water in the gasifier thereby providing a gasi-fied stream containing carbon monoxide, hydrogen and nitrogen, passing the gasified stream and an ionizing seed material to a burner and there contacting the gasified stream with preheated air to burn the gasified stream thereby producing ionized combustion gases having a tempera-ture greater than about 3600°F., accelerating the ionized combustion gases to a velocity greater than about 400 meters per second, passing the accelerated ionized combustion gases through an MHD generator to generate DC power and thereafter through a diffuser to reduce the gas velocity, and passing the gases from the diffuser in heat exchange relationship with the gasifier to provide heat to sustain the endothermic reaction of carbon and water.
introducing carbonaceous material and water to a gasifier, initiating and sustaining the endothermic reaction of carbon and water in the gasifier thereby providing a gasi-fied stream containing carbon monoxide, hydrogen and nitrogen, passing the gasified stream and an ionizing seed material to a burner and there contacting the gasified stream with preheated air to burn the gasified stream thereby producing ionized combustion gases having a tempera-ture greater than about 3600°F., accelerating the ionized combustion gases to a velocity greater than about 400 meters per second, passing the accelerated ionized combustion gases through an MHD generator to generate DC power and thereafter through a diffuser to reduce the gas velocity, and passing the gases from the diffuser in heat exchange relationship with the gasifier to provide heat to sustain the endothermic reaction of carbon and water.
2. The method of claim 1, wherein the mixture in the gasifier is maintained at a temperature in the range of from about 1300°F. to about 2500°F.
3. The method of claim 1, wherein the seed material is potassium sulfate or potassium carbonate.
4. The method of claim 1, wherein the preheated air enters the burner at a pressure in the range of from about 20 psi to about 150 psi.
5. The method of claim 1, wherein the preheated air enters the burner at a temperature in the range of from about 500°F. to about 3000°F.
6. The method of claim 1, wherein the ionized combus-tion gases leave the burner at a temperature in the range of from about 3600°F. to about 6000°F.
7. The method of claim 1, wherein the ionized combus-tion gases are accelerated to a velocity in the range of from about 400 meters per second to about 1100 meters per second.
8. The method of claim 1, wherein the gases entering the MHD generator are substantially free of ash.
9. The method of claim 1, wherein the velocity of the gases leaving the diffuser is about 100 meters per second.
10. The method of claim 1, wherein the temperature of the gases leaving the diffuser is about 1000°F. less than the temperature of the gases entering the MHD generator.
11. The method of claim 1, and further comprising pass-ing at least a portion of the gases from the diffuser in heat exchange relationship with water to produce steam for transmittal through a steam turbine to generate AC power.
12. A method of generating electrical power, comprising:
introducing carbonaceous material and water to a gasifier, heating the mixture of carbonaceous material and water to initiate and sustain the endothermic reaction of carbon and water thereby providing a gasified stream containing carbon monoxide, hydrogen and nitrogen, passing the gasified stream and an ionizing seed material and air from a pre-heater to a burner to burn the gasified stream thereby pro-ducing ionized combustion gases having a temperature greater than about 3600°F., accelerating the ionized combustion gases to a velocity greater than about 400 meters per second, passing the accelerated ionized combustion gases through an MHD generator to generate DC power and thereafter through a diffuser to reduce the gas velocity, passing the gases from the diffuser to an afterburner to burn same, and passing the gases from the afterburner in heat exchange relationship with the gasifier to provide heat to sustain the endothermic reaction of carbon and water and with the preheater to pre-heat the air prior to combustion with the gasified stream.
introducing carbonaceous material and water to a gasifier, heating the mixture of carbonaceous material and water to initiate and sustain the endothermic reaction of carbon and water thereby providing a gasified stream containing carbon monoxide, hydrogen and nitrogen, passing the gasified stream and an ionizing seed material and air from a pre-heater to a burner to burn the gasified stream thereby pro-ducing ionized combustion gases having a temperature greater than about 3600°F., accelerating the ionized combustion gases to a velocity greater than about 400 meters per second, passing the accelerated ionized combustion gases through an MHD generator to generate DC power and thereafter through a diffuser to reduce the gas velocity, passing the gases from the diffuser to an afterburner to burn same, and passing the gases from the afterburner in heat exchange relationship with the gasifier to provide heat to sustain the endothermic reaction of carbon and water and with the preheater to pre-heat the air prior to combustion with the gasified stream.
13. The method of claim 12, wherein the carbonaceous material is selected from the class consisting of coal, oil shale, tar sands, forest waste material, farm and municipal waste material, wood, lignite and peat and mixtures thereof.
14. The method of claim 12, wherein the carbonaceous material is coal.
15. A method of generating electrical power, compris-ing: introducing coal and water to a gasifier, heating the mixture of coal and water to initiate and sustain the endothermic reaction of carbon and water thereby providing a gasified stream containing carbon monoxide, hydrogen and nitrogen, providing a compressor for compressing air and a preheater for preheating air, passing the gasified stream and an ionizing seed material and compressed preheated air having a temperature of up to about 3000°F. and a pressure of up to about 150 pounds per square inch to a burner to burn the gasified stream thereby producing ionized combus-tion gases having a temperature in the range of from about 3600°F.to about 6000°F., accelerating the ionized combus-tion gases to a velocity in the range of from about 400 meters per second to about 1100 meters per second, passing the accelerated ionized combustion gases through an MHD
generator to generate DC power and thereafter through a diffuser to reduce the gas velocity, passing the gases from the diffuser to an afterburner to burn same, and passing the gases from the afterburner in heat exchange relation-ship with the gasifier to provide heat to sustain the endo-thermic reaction of carbon and water and in heat exchange relationship with the preheater to provide heat for pre-heating air and extracting energy from the gases from the afterburner for energizing the compressor.
generator to generate DC power and thereafter through a diffuser to reduce the gas velocity, passing the gases from the diffuser to an afterburner to burn same, and passing the gases from the afterburner in heat exchange relation-ship with the gasifier to provide heat to sustain the endo-thermic reaction of carbon and water and in heat exchange relationship with the preheater to provide heat for pre-heating air and extracting energy from the gases from the afterburner for energizing the compressor.
16. The method of claim 15, wherein the coal and water are added to the gasifier at ambient temperatures.
17. The method of claim 15, wherein the gasified stream leaving the gasifier is at a temperature less than about 2000°F. and the air leaving the compressor is at a temperature of about 500°F. and at a pressure of about 70 psi and the air leaving the preheater is at a temperature of about 3000°F, and the ionized combustion gases leave the burner at a temperature in the range of from about 5000°F.
to about 5500°F.
to about 5500°F.
18. The method of claim 17, wherein the ionized combustion gases are accelerated to a velocity of about 1100 meters per second and the gases leaving the diffuser have a velocity of about 100 meters per second and a temperature in the range of from about 4000°F.to about 4500°F.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/177,327 US4345173A (en) | 1980-08-12 | 1980-08-12 | Method of generating electricity using an endothermic coal gasifier and MHD generator |
| US177,327 | 1980-08-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1157910A true CA1157910A (en) | 1983-11-29 |
Family
ID=22648176
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000382684A Expired CA1157910A (en) | 1980-08-12 | 1981-07-28 | Method of generating electricity using an endothermic coal gasifier and mhd generator |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4345173A (en) |
| JP (1) | JPS57110071A (en) |
| CA (1) | CA1157910A (en) |
| DE (1) | DE3131921A1 (en) |
| FR (1) | FR2488751B1 (en) |
| GB (1) | GB2081984B (en) |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4516043A (en) * | 1980-10-16 | 1985-05-07 | The Regents Of The University Of California | Method and apparatus for generating electrical energy from a heated gas containing carbon particles |
| US4851722A (en) * | 1986-09-24 | 1989-07-25 | Coal Tech Corp. | Magnetohydrodynamic system and method |
| US5055724A (en) * | 1989-10-30 | 1991-10-08 | United States Department Of Energy | Open-cycle magnetohydrodynamic power plant with CO2 recycling |
| US5260640A (en) * | 1992-01-28 | 1993-11-09 | The United States Of America As Represented By The United States Department Of Energy | Method of and system for producing electrical power |
| US5254934A (en) * | 1992-01-28 | 1993-10-19 | The United States Of America As Represented By The United States Department Of Energy | Method of and system for producing electrical power |
| JP2004229374A (en) * | 2003-01-21 | 2004-08-12 | Hokkaido Univ | Method for mhd single high efficient power generation and system |
| US7241322B2 (en) * | 2003-11-21 | 2007-07-10 | Graham Robert G | Pyrolyzing gasification system and method of use |
| US8182560B2 (en) * | 2007-08-29 | 2012-05-22 | Kaufman Thomas W | Method for gasifying hydrocarbon materials for the production of hydrogen |
| AU2011213604B2 (en) * | 2010-02-08 | 2014-07-31 | Shell Internationale Research Maatschappij B.V. | Power plant with magnetohydrodynamic topping cycle |
| US8277543B2 (en) * | 2010-12-02 | 2012-10-02 | Bert Zauderer | Fossil fuel fired, closed cycle MHD generator in parallel with steam turbine cycle with zero emissions and CO2 sequestration |
| WO2013025625A1 (en) * | 2011-08-15 | 2013-02-21 | Bert Zauderer | Terrestrial power and propulsion from nuclear or renewable metal fuels with magnetohydrodynamics |
| US9080768B2 (en) | 2012-11-08 | 2015-07-14 | General Electric Company | Gasifier preheater fuel system and methods of assembling same |
| US9004911B1 (en) * | 2012-11-29 | 2015-04-14 | U.S. Department Of Energy | Apparatus and method for solid fuel chemical looping combustion |
| US11215360B2 (en) * | 2015-08-18 | 2022-01-04 | Glock Ökoenergie Gmbh | Method and device for drying wood chips |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1118041A (en) * | 1964-07-07 | 1968-06-26 | Conch Int Methane Ltd | Improvements in and relating to thermal power plants |
| GB1072630A (en) * | 1964-12-18 | 1967-06-21 | Int Research & Dev Co Ltd | Improvements in and relating to magnetohydrodynamic electricity generating systems |
| FR1492980A (en) * | 1966-06-30 | 1967-08-25 | Alsthom Cgee | Improvement in open magnetohydrodynamic cycles |
| PL69424B1 (en) * | 1970-01-20 | 1973-02-28 | ||
| US4163910A (en) * | 1977-01-31 | 1979-08-07 | Combustion Engineering, Inc. | Vapor generator and MHD power plant |
| US4282449A (en) * | 1979-08-03 | 1981-08-04 | Combustion Engineering, Inc. | Coal gasifier supplying MHD-steam power plant |
-
1980
- 1980-08-12 US US06/177,327 patent/US4345173A/en not_active Expired - Lifetime
-
1981
- 1981-07-28 CA CA000382684A patent/CA1157910A/en not_active Expired
- 1981-08-03 GB GB8123700A patent/GB2081984B/en not_active Expired
- 1981-08-12 FR FR8115638A patent/FR2488751B1/en not_active Expired
- 1981-08-12 JP JP56126557A patent/JPS57110071A/en active Pending
- 1981-08-12 DE DE19813131921 patent/DE3131921A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| JPS57110071A (en) | 1982-07-08 |
| DE3131921A1 (en) | 1982-08-19 |
| GB2081984A (en) | 1982-02-24 |
| FR2488751A1 (en) | 1982-02-19 |
| US4345173A (en) | 1982-08-17 |
| GB2081984B (en) | 1984-09-05 |
| FR2488751B1 (en) | 1985-06-14 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |